Interactions of adherent-invasive Escherichia coli with human colonic epithelium

Evans, Bethan Fay (2025) Interactions of adherent-invasive Escherichia coli with human colonic epithelium. Doctoral thesis, University of East Anglia.

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Abstract

Adherent-invasive Escherichia coli (AIEC) is associated with Crohn’s Disease (CD), a type of inflammatory bowel disease (IBD) affecting over 120,000 people in the UK. AIEC have been shown to adhere to and invade epithelial cell lines and replicate within macrophages but their interaction with fully differentiated human intestinal epithelia remains largely unexplored. Here, the pathogenesis of AIEC prototype strain LF82 was investigated using differentiated human colon carcinoma cell lines and patient-derived colonic organoids.

While LF82 adherence and biofilm formation was significantly increased compared to non-pathogenic E. coli MG1655, invasion and intracellular replication were comparable in both strains. Notably, LF82 binding was mediated by type I fimbriae but occurred independently of the established AIEC receptor CEACAM-6. Despite low invasion and intracellular replication, infection with LF82 resulted in cytotoxicity which was dependent on bacterial contact but not invasion or type VI secretion of effector proteins. Similar to CD, LF82-infected colonic epithelia exhibited reduced barrier function and increased release of TNF-α, IL-6 and IL-8.

Extension of these studies to other AIEC isolates demonstrated highly divergent infection strategies. Overall, these results suggest that AIEC LF82 pathogenesis in the human colon is strain-specific and mediated by the formation of biofilms, contact-dependent cytotoxicity, epithelial permeability, and pro-inflammatory cytokine secretion.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User:	Chris White
Date Deposited:	26 Feb 2026 11:27
Last Modified:	26 Feb 2026 11:27
URI:	https://ueaeprints.uea.ac.uk/id/eprint/102075
DOI:

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